Electromagnetic reed unit for electrical musical instruments



l`lune 5, 1951 l A/n H ow H. E. ROGERS E' AL ELECTROMAGNETIC REED UNITFOR ELECTRICAL MUSICAL INSTRUMENTS Filed Feb; 26, 1948 Fig. 2.

a "III'IIIIIA'IIIIIL l i /9 /5/4 l0 20 A L /q Fig. 5.

\ l0 Haro/d E.- Rogers L ,6 John M. Mag/da INVE'NTOR- Patented June 5,1951 ELECTROMAGNETIC REED UNIT FOR ELEC- TRICAL MUSICAL INSTRUMENTSHarold E. Rogers. Los Angeles, and John M. Magida, North Hollywood,Calif.

Application February 26, 1948, Serial No. 11,066

Claims.

This invention relates to electrical musical instruments using steelreeds for producing musical tones and it has particular reference to thetranslation of the mechanical oscillations of the steel reed intoelectrical oscillations.

The main object of the invention is to provide an improved translationunit, which is simple, effective .and compact and which improvesmarkedly the quality of the tone obtainable by retranslation of theelectrical oscillation into sound waves.

A further object of the invention consists in eliminating fromelectrical reproduction all external influences, not manifestingthemselves in the oscillations of the reed itself and due partly to themethod of starting the oscillations by means of an air current andpartly to disturbances in the Vicinity of the reed, so that the waves ofthe electrical currents produced represent solely the fundamentaloscillation of the reed and their harmonics.

A further object of the invention consists in making the oscillations ofa reed most effective for faithful current production by using amagnetized reed, oscillating in the interior of a coil.

A further object of the invention consists in rendering the oscillationsof the reed most effective for faithful current production by arranginga ilat reed inside of a coil consisting of windings which are arrangedin substantial parallelism to the plane of the flat reed on both sidesof the same.

A further object of the invention consists in rendering the oscillationsof the reed most effective for current production and in securing a highdelity of reproduction by using a ilat reed arranged on the inside of acoil in a plane approximately bisecting the height of the coil with thewindings arranged in planes parallel to the plane of the reed.

A further object of the invention consists in providing a compact unitof high eiciency by using an insulating frame closely surrounding theoscillating reed having walls reduced to a minimum around the end of thereed.

Further more specific objects will be apparent from the detailedspecication.

In known electrical instruments using vibrating reeds for producingmusical tones of a desired pitch, quality, timbre or othercharacteristics, musical tones are customarily produced by blowing airagainst oscillating reeds. The mechanical oscillations of the reedproduce an air vibration manifesting itself as a tone which is thentranslated into electrical oscillations by some electroacoustic meanssuch as a microphone. In most cases, however, this tone is at leastpartly contaminated by undesirable noises produced by the rushing airblowing against the reeds and .also by the control mechanism of the airjets such as keys, flaps, valves, etc. which all produce sounds uponbeing moved or upon coming to a stop.

It is therefore desirable that the electroacoustic apparatus be replacedfor instance, by an electrostatic or electromagnetic translationapparatus. However devices of this type are mostly not satisfactory asthey are selective .and do not furnish a perfect reproduction of thereed oscillations.

According to the invention an electromagnetic device is used whichfurnishes an approximately perfect translation of the natural reedvibration, comprising not only a fundamental oscillation, but also anumber of overtones. The essence of the invention consists in placing acoil in a magnetic field produced by and surrounding the magnetizedvibrating reed, the reed oscillations in this case changing thereluctance of the' path of the magnetic field of the magnetized reed.The change in the eld induces an oscillation in the coil correspondingexactly to the reed oscillation.

The inventive concept is best described by referring to the accompanyingdrawing showing one embodiment thereof. It is however to be understoodthat this particular embodiment is to be regarded as an example servingthe purpose of explaining the principle of the invention and `apreferred mode in which it is contemplated applying this principle. Theinformation supplied when describing this example will enable expertsskilled in this art to construct further embodiments of the inventionand modifications of the example described and sho-wn are therefore notnecessarily departures from the invention.

In the drawing:

Figure l is a perspective sectional view of a unit according to theinvention, on a much enlarged scale showing part of the unit broken awayand a transverse section at the point where it is broken.

Figure 2 is a plan View of the unit.

Figure 3 is a sectional elevational View of the unit, the longitudinalsection being taken `along line 3 3 in Figure 2.

Figure 4 is a sectional elevational View the section being taken alongline 4-4 in Figure 2.

Figure is a sectional elevational view the section being taken alongline 5-5 in Figure 2.

Figure 6 shows the direction of the air flow which is blown through thechannel.

The unit according to the invention comprises the reed I0 which consistsof magnetized steel and of a reed holder or carrier frame I2 of anapproximately rectangular prismatic shape surrounding the reedcompletely and enclosing it between its walls. The reed is held in aplane coinciding with or adjacent to the median plane of symmetrybisecting the height of the open prismatic reed holder frame I2. I4 atone end of the frame I2 forms the base on which the reed is attached bymeans of a screw I5.

The outer walls of the prismatic reed holder frame are at and carry acoil 29 to be described below. The inner wall projects towards the reedvso as to surround .it very closely in the middle portion of the frame.The end portions of the 'frame are however elliptically gouged (at I8)so as to recede from the reeds, but near the edge of the reed a ledge I6is projecting the upper surface of which is approximately coincidingwith the reed surface.

The walls are made as thin as possible in order to reduce the distancebetween the magnetized reed I0 and the coil 20 as much as possible. Thegouging of the end permits a further reduction of the end wall I9 nearthe tip of the reed, which has the largest amplitude.

The coil 20 surrounding the frame I2 is of fine insulated closely woundcopper wire applied in one or more layers and the ends of the coil wireare fixed to two terminal posts 2 I, 22, arranged at one end of theframe I2 which are provided with means for making connection with theoperative circuits. The number of turns of the coil must be so chosenthat the desired amplitude of the electrical current results when thereed is brought to oscillation.

'I'he unit above described is located above a blow pipe (not shown) suchas conventionally used having its orifice below the gouged end portionI8 of the frame. The air blown against the tip of the reed produces itsoscillation.

In operation the reed is brought to oscillation by the stream of airblowing through the gouged end I8 of the frame I2 towards the reedclosely surrounded by the ledge ifi. There is however a suiiciently widepath for the escape of the air when the reed is lifted thereby wideningthe gap between it and the ledge. The reed thus deflected starts itsoscillation with its natural frequency determined by its free length.The oscillation of the reed produces a periodic variation of thereluctance of the path of the magnetic iield and the resulting variationof the magnetic flux vtraversing the coil induces an electric current inthe coil which is inversely proportional to the ux density (in gauss)prevailing in the area between the edges of the reedand the inner coilsurface and to the length of wire (in cm.)

This current is solely dependent on the movement of the reed andtherefore solely reproduces the vibratory movement to which it issubjected. All external Sources of disturbance are therefore withoutinfluence and are eliminated from reproduction. The current, therefore,varies merely n accordance with the fundamental oscillation and itsharmonics as produced by the reed.

The current is then amplied and reproduced in a speaker or a similartranslating device in the conventional manner.

A cross piece The coil 20 of very fine insulated copper wire is woundevenly around the outer surface. However the coils on the reeds ofshorter length, oscillating with higher frequency, are provided with alarger number of turns in order to increase their electrical output andalso their inductance to obtain uniform electric characteristics in allthe units of an instrument.

It will be clear that 'variations or changes relating to the unessentialdetails will not in any way affect the essence of the invention.

Having described the invention, what is claimed as new is:

1. A unit for producing oscillatory electric currents corresponding tomusical tones for use in electrical musical instruments, with a flat,elongated reed of magnetized ferro-magnetic material of a lengthcorresponding to the tone to be produced, adapted to be set intooscillation by a current of air blown against it, comprising a prismaticframe of insulating material with a prismatic hollow interior spaceforming a channel encircling the `feed completely, one cross section ofsaid channel being approximately lled by said reed, said channel beingthus substantially subdivided into two compartments by the reed, whileadapted to conduct the air in a direction at right angle to the saidcross section, a coil of ne insulated wire consisting of windingssurrounding said frarne and encircling the zone occupied by the reed,said windings engendering cuirents upon variations of the magnetic eldproduced by the oscillation of the reed in the interior or the coil.

2. A unit'for producing oscillatory electric currents corresponding tomusical tones for use in electrical musical instruments, with a thin,ilat elongated, freely oscillating reed of magnetized ferro-magneticmaterial, of a free length corresponding to the frequency of the 'toneto be produced, adapted to be set into oscillation by a current of airblown against it, comprising a substantially prismatic frame ofinsulating material with a prismatic hollow interior space forming achannel encircling the reed completely, one cross section of the channelbeing approximately iilled by the reed, said channel being thussubstantially subdivided into 'two compartments by the reed, whileadapted to conduct the air in a direction at right angle to the crosssection lled by the reed, said frame being provided with a stepped seatportion on its inner side, projecting into the interior of the elongatedchannel at one end thereof for xedly supporting one end of said reed,the walls of the frame projecting in wardly towards the reed beingreduced to a minimum thickness in the portion surrounding the free endof the reed, a coil of fine insulated wire consisting or windingssurrounding said frame and encircling the space occupied by the reed,said windings engendering currents upon variations of the magnetic fieldproduced by the oscillation of the reed in the interior of the coil.

3. A unit for producing oscillatory electric currents corresponding tomusical tones for use in electrical musical instruments, with a freelyoscillating, thin, flat elongated reed of magnetized ferro-magneticmaterial of a free length corresponding to the frequency of the tone tobe produced and adapted to be set into oscillation by a current of airblown against it, comprising a substantially prismatic frame ofinsulating material with a prismatic hollow interior space forming achannel encircling the reed closely and completely, one cross section ofsaid channel being approximately lled by said reed, said channel beingopen for the passage of air through it in the direction at right anglesto the plane of the cross section nlled by the reed, said elongatedprismatic frame being provided with a stepped seat portion near one ofits ends, forming' a seat for Xedly supporting the reed and being gougedabove and below a middle zone close to the cross section filled by thesaid reed and near the freely oscillating end portion o1 the reed toreduce the thickness of the walls near said freely oscillating endportion of the reed, a coil of line insulated wire wound around theframe and consisting of windings arranged in planes substantiallyparallel to that of the reed, and further arranged above and below thereed so that the plane of the reed approximately bisects the height ofthe coil, said windings engendering currents upon variations of themagnetic eld or" the reed produced by its oscillation in the interior ofthe coil.

4. A unit for producing oscillatory currents corresponding to musicaltones for use in elecrical instruments, comprising an elongatedprismatic frame of substantially rectangular cross section, open at itsends and surrounding an elongated substantially rectangular hollow spaceforming an air conducting channel extending axially at right angles tothe said cross section, a flat elongated reed of magnetizedferro-magnetic material substantially lling a cross sectional area ofsaid channel and held for transverse free oscillation within saidchannel at a point intermediate between the open ends of the frame, acoil wound around said prismatic frame around the zone containing thecross section substantially lled by the reed, and means for producingfree oscillations of said reed, within the interior of the coil, whichin their turn produce currents within the coil exactly proportional tosaid oscillations.

5. A unit for producing oscillatory currents corresponding to musicaltones for use in electrical musical instruments, comprising an elongatedprismatic frame of substantially rectangular cross section open at itsends and surrounding an elongated substantially rectangular hollow spaceforming an air conducting channel extending axially at right angles tosaid cross section, a thin, Hat, elongated reed of magnetizedferromagnetic material of substantially rectangular shape, its lengthbeing a multiple or its width and the latter being a multiple of itsthickness, the said reed being arranged within and approximately lling across sectional area of the said air conducting channel formed by thehollow interior of the prismatic frame, said reed being held in aposition in which it is parallel to the basis of the prismatic frame,seating means on one end of said prismatic frame on the interiorthereof, projecting into said hollow space at a point intermediatebetween the open ends oi said frame for xedly supporting one end of thereed, the projecting portion of the reed being free for oscillationwithin the channel, and a coil surrounding the said prismatic frame inthe Zone in which the reed is supported, the reed thus oscillatingWithin the coil around a plane which is substantially perpendicular tothe axis of the coil` HAROLD E. ROGERS. JOHN M. MAGIDA.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,026,342 Curtiss Dec. 31, 19352,119,584 Knoblaugh June 7, 1938 2,151,021 Frohman Mar. 2l, 19392,330,261 Beyer Sept, 28, 1943 2,383,553 Johnson Aug. 28, 1945

